Parallel plate capacitors have been in manufacture for many years. The basic design of these capacitors involves two conductive electrodes separated by a dielectric or insulative thin film material. While many variations of this type of capacitor have been developed, all of the known designs suffer from the following disadvantages. One of these disadvantages is the condition wherein a small defect in the dielectric layer wherein the two electrodes are allowed to short together. This short circuit renders the entire capacitor useless, resulting in loss of product. A second disadvantage is the inability to take a single sheet of capacitor material (formed of a sandwich of conductive material on the outside and thin film dielectric material on the inside), and cut this material into several smaller value capacitors and attaching connectors to the conductive portions of these smaller value capacitors. This inability is due to the shorting out of the conductive layers by the cutting, shearing or connecting action itself that creates defects in the dielectric, resulting in high leakage and potential shorts. The present invention overcomes these disadvantages by providing discrete locations of electrode interaction, thereby allowing failure points to be removed, as well as allowing a simple method of forming capacitors with specific capacitance. Furthermore, due to the reduced active electrode area, capacitors with small capacitance can be formed while still allowing enough surface area for connecting the capacitor to other circuitry. These thin dielectrics, if ferroelectric, such as barium strontium titanate (BST), can have the capacitance varied by applying a bias voltage. The thinner the dielectric, the lower the bias voltage can be to effect the same capacitance change. These tunable capacitors have a wide range of applications particularly in the RF wireless arena.
In the field of tunable capacitors that use ferroelectric dielectrics, a particular problem is intermodulation distortion (IMD), that can occur as the RF electric field inadvertently biases the material at the RF frequency. This problem is addressed by the present invention by providing several embodiments of capacitor electrodes that allow greater levels of tunability, while reducing RF interaction with the biasing electrodes.